Vehicular seats currently used in combat vehicles are unfortunately of such a basic and simplistic design as to lack support systems and blast protection to mitigate the incidence and magnitude of injuries to the soldiers and other personnel that utilize such vehicles in combat zones. Even aside from the obvious dangers imposed on the personnel by attacks on the vehicles, including by enemy use of such weapons as so called “improvised explosive devices” (“IEDs”), combat troops are also exposed to a range of serious injuries during high speed convoy movement of personnel carriers with increased risk of serious spinal injuries and deaths. Frequent convoy deceleration thus results in rear-end collisions; even at slowed speed serious whiplash injury results. High-speed patrols on pot-holed, “wash board” and dirt roads result in repetitive jarring to soldiers resulting over time in spine injuries and brain trauma.
With respect to civilian transportation, increasing efforts have in recent years been made by manufacturers and governmental regulation to prevent or minimize injuries sustained by automobile passengers during accidental collisions. In such regard the present inventor in a series of inventions has disclosed seat constructions which serve to minimize or prevent the whiplash and similar injuries that occur upon rear end impact at a vehicle in which the passenger is riding. These inventions are disclosed in a number of issued patents of the present inventor, including in U.S. Pat. Nos. 5,181,763; 5,290,091; and 5,580,524. The disclosures of the foregoing patents are incorporated herein by reference and constitute important background for the present invention, in that certain of the principles taught therein are synergistically combined in the present invention with further elements to provide a new instrumentality applicable to the vastly more complex and dangerous combat environment to which the invention is applicable.
It may be noted here that certain faulty premises continue to exist regarding rear-end, low-speed collisions. One of these is that whiplash injury is caused by a typical hyperextension movement of the head and neck. In the normal extension movement, the head rotates on the vertebra below C1, C1 rotates over the instantaneous axis of rotation of C2, and then C2 rotates on the C3 instantaneous axis of rotation, and so on until the entire cervical spine completes its full extension motion. In rear-end collisions, this pattern of extension motion does not occur; rather, a completely unnatural motion is observed when high-speed x-ray is used to observe human aberrant spinal kinematic motion. These studies observe axial loading from thoracic spine straightening, causing impaction of the cervical facet plates above and, then, hyperextension of the lower cervical vertebrae rotating and compressing each vertebra from under the vertebra above. This is initiated by the seat back, which is sweeping the lower portion of the neck under the upper portion of the neck. This results in an abnormal double harmonic curve in the cervical spine often referred to as the dreaded “S” curve.
Investigation has contributed to the understanding of injury mechanism by identifying the zygapophyseal joint as the source of pain in 54% of patients with chronic neck pain after whiplash injury. With the zygapophyseal joint identified as the primary injury site, the next development was observation of what happened to these cervical joints during the rear-end impact event on human volunteers. This was accomplished with cineradiography, which showed significant aberration in motion during rear-end impact, resulting in facet plate collision and impingement. Increased shear force and extension motion to the lower cervical vertebra was observed while the upper portion of the cervical spine followed the head into flexion, giving the formation of an “S” curve. The transition area of the S curve was at the level of C4, C5, and C6, the most common injury sites observed in a whiplash victim in postaccident x-ray analysis.
Many variables can influence the forces to the spine that can cause injury: the size of the vehicles, the size of the occupants, and the speeds of the vehicles. Attempting to prevent whiplash injury thus can be a daunting task. However, reducing the global movement of the entire spine and the relative movement of each vertebra appear to be the most practical approach in the prevention of injury to the spine. To accomplish this, all spinal curves should be supported and decelerated at as close to a zero delta velocity as possible. This requires support systems within head-neck restraints and seats that are contoured to the spine to reduce the spinal straightening observed during rear end impact. Additionally, the head-neck restraint and seat back should have complementary dampening characteristics so that simultaneous deceleration of the head, neck, thoracic, and lumbopelvic areas can be achieved.
In my issued U.S. Pat. Nos. 5,181,763 and 5,290,091, apparatus is disclosed for preventing whiplash-related injuries to a passenger in a vehicle. The characteristic shapes of the devices shown therein define a supporting means and contour located behind the cranium and cervical spine of the passenger that interfit with the posterior contour of the passenger's cranium and cervical spine. The supporting means interacts with the passenger during rear end impact to maintain the pre-collision shape of the supported spinal curves, to thereby aid in the avoidance of whiplash and similar injuries. The support contour basically presents a first surface located behind the seated passenger's cranium for contacting the approximate center of mass of the cranium and supporting the approximate central posterior area of the seated passenger's cranium, and a second surface located below the first surface and defining a substantially convex smooth curve, a maximum protrusion point of which in the direction of passenger support projects anteriorly relative to where the first surface contacts the center of mass of the related passenger's cranium, said second surface thereby contacting and supporting the posterior portion of the seated passenger's cervical spine substantially simultaneously with the contact of the seated passenger's cranium with said first surface;
In my further issued U.S. Pat. No. 5,580,124 there is disclosed a vehicle-installed supporting seat for a passenger, which includes a seat back provided with an integral head-neck restraint comprising a cranium support portion and a cervical spine support portion. Each said portion includes a layer of resilient material supported on an underlying inflexible support shell, which together act to effectively define a contour that interfits with the posterior contour of the passenger's cranium and cervical spine. The support shell is rearwardly displaceable upon being subjected to impressed forces generated from the passenger pressing against the restraint as a result of a rear end impact at said vehicle. A controllably deformable energy absorbing crush zone is disposed to the rear of the shell as to be compressed by the rearward displacement of the shell. The interfitting contour and thereby the inflexible shell, upon being displaced by said forces toward the underlying crush zone, retain the shape of the contour, whereby the cervical and cranium support portions act to substantially simultaneously decelerate the cranium and cervical spine of the passenger during a vehicle rear end impact, while the controlled deformation of the crush zone absorbs energy, to prevent whiplash-related injuries to the passenger.
The apparatus of the U.S. Pat. No. 5,580,124 patent preferably further includes a thoracic and lumbar spine support portion which are defined by downward extension of the support shell, resilient material and contour; whereby the thoracic and lumbar spine portion of the passenger are decelerated with the cranium and cervical spine during a rear end impact.
The thoracic section of the human spine is believed to be compressed and flattened during a rear end impact. In addition to being injured, this flattening of the thoracic spine causes axial loading into the cervical spine as the weight of the head and upward pressure of the flattening thoracic spine serve as end point forces to damage the cervical spine. Where present, the thoracic portion of the above seat serves to prevent the flattening of the thoracic spine by having a kyphotic or concave firm contoured shell that takes the shape of the human thoracic spine and maintains this shape during rear end impact. This firm contoured shell precedes the crush zone material which plastically deforms and produces a controlled damping of the forces incurred during a rear end collision.
The lumbar section of the seat will conform to the lumbar spinal curves of the human anatomy. The initial foam that contacts the occupants is combined with the crush zone feature to maximize the energy-absorbing feature of this technology.
It is essential that upon a rear impact at the vehicle, a relatively inflexible surface which approximately conforms to the spine of the seated passenger (herein referred to as the “shaped surface”) provides a restraining boundary which maintains the normal curvature of the spine; this despite the fact that the passenger will be subjected to large forces generated by the impact which would otherwise rearwardly accelerate the passenger with respect to the vehicle as a frame of reference.